Chirped Laser Dispersion Spectroscopy (CLaDS) provides a measure of optical dispersion resultant from the interaction of laser light with the molecular transitions of a target species. To probe optical dispersion, a multi-frequency (e.g. two or three color) beam is generated with a well-defined frequency spacing. When the different frequency components interact with the resonant transition, each component experiences a different index of refraction. At the detector, optical heterodyne detection is performed, and the dispersion effects are retrieved through measurements of the instantaneous frequency of the beatnote signal. The sample dispersion spectrum can be used to identify the sample and to determine its concentration. What is needed are systems and methods for direct improvement of SNR of the instrument. This would result in lower chemical detection limits and improved sensitivities of instrumentation for detection of important trace gases in environmental, industrial, and medical applications particularly in systems implemented in free space with long sample arm lengths.